For electron gain enthalpies of the elements denoted as Δ_(eg) H, the incorrect option is :

Solution

Chemistry ma’am · 3 steps

Read every < with the minus sign kept: more negative means smaller. Only one inequality fails that test.

1. Signed comparison. Electron gain enthalpies here are negative numbers. So Δ_(eg)H(X) < Δ_(eg)H(Y) means X releases more energy than Y when it takes an electron.
2. Two group trends. Down a group the atom gets bigger, so the value usually becomes less negative. The exception is the period 2 element: F and O are so small that their crowded 2p shell repels the incoming electron. So Cl is more negative than F, and S is more negative than O. From S downwards the normal trend holds.

   Option	Values (kJ mol⁻¹)	Is the inequality true?
   (a) I < At	-295 < -270 (At about)	true
   (b) Te < Po	-190 < -174	true
   (c) Cl < F	-349 < -328	true
   (d) Se < S	-195 < -200	false

3. So. Sulphur releases more energy than selenium, so Δ_(eg)H(S) < Δ_(eg)H(Se). The incorrect option is (d).

The idea to keep. Down a group, electron gain enthalpy becomes less negative. The only exception is the period 2 element: Cl beats F and S beats O. Always compare the signed values.

Answer from the NTA final answer key. Solution by PrepWiser.